This invention relates generally to air bag cover assemblies and more particularly to air bag cover assemblies that have an "invisible" air bag door beneath a covering that is torn open when the air bag door is pushed open by an inflating air bag.
The covering usually comprises a thin flexible skin of polyvinyl chloride and an underlying layer of resilient polyurethane foam although other suitable thermoplastic materials may be used for the skin and the foam.
These cover assemblies may include piercing or cutting devices that are actuated by the inflating air bag to assist in piercing and tearing through the covering when the invisible air bag door is pushed opened.
For instance U.S. Pat. No. 5,035,444 granted to James Carter Jul. 30, 1991 discloses a cover assembly that includes a single pivotal cutter with three blade edges disposed beneath an invisible air bag door. The inflating air bag pivots the cutter outwardly pushing the blade edges up to cut through the foam layer and outer skin of the covering before the air bag door is pushed open. The cutter is bent for self retainment against a windshield following air bag deployment to shield the cutting edges from passenger contact.
U.S. Pat. No. 5,046,758 granted to Scott Rafferty, Bruce Batchelder and Mark Dupris Sep. 10, 1991 discloses a cover assembly that includes several pivotal cutters disposed beneath an invisible air bag door. These several cutters are also pivoted up by the inflating air bag to cut through the foam layer and outer skin of the covering to release the air bag door. The cutters are arranged to self retract to their initial position in the cover assembly following air bag deployment to shield the cutting edges from passenger contact.
While these arrangements are satisfactory for their intended purpose, the arrangements require special provisions as noted for shielding the cutting edges from passenger contact. This is because the arrangements rely on an extension principle where cutting edges are pushed up relative to the air bag door through the foam layer and skin of the covering.